Integrated implantable hearing device, microphone and power unit

ABSTRACT

An implantable hearing unit is provided that includes an implantable microphone, a rechargeable power storage device and a speech signal processor. The hearing unit further includes a signal coupling device that is adapted for electrical interconnection to an implantable auditory stimulation device, which is operative to stimulate an auditory component of a patient. Such a stimulation device may include cochlear implants, brain stem stimulation systems, auditory nerve stimulation systems, and middle or inner ear transducer systems. The signal coupling device is operative to provide processed drive signals from the signal processor to the stimulation device as well provide power from the power storage device to operate the stimulation device. In one arrangement, the signal coupling device is a wireless coupling between first and second coils. In such an arrangement, the hearing unit may be utilized with an existing implanted stimulation device to make that device a fully implanted hearing system.

RELATED APPLICATIONS

The present application is a divisional of and claims priority to U.S.patent application Ser. No. 11/356,434, filed Feb. 16, 2006, which inturn claims priority to U.S. Provisional Patent Application No.60/653,415, the present application also claiming priority thereto, thedisclosures of which are hereby incorporated by reference herein inentirety.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119 to U.S.Provisional Application No. 60/653,415 entitled “Integrated ImplantableHearing Device Microphone and Power Unit” and having a filing date ofFeb. 16, 2005, the entire contents of which are incorporated byreference herein.

FIELD OF THE INVENTION

The present invention relates to implanted hearing devices, and moreparticularly, to an implanted microphone and power unit assembly for usewith an implantable stimulation device attached to a patient's auditorysystem.

BACKGROUND OF THE INVENTION

Implantable hearing devices stimulate internal components of theauditory system and are generally classified into one of two types,namely fully implantable hearing aids and semi-implantable hearing aids.In a fully implantable hearing device, the entire device is implanted.In a semi-implantable hearing device, some of the components, typicallythe microphone, power supply, and speech signal processor, areexternally worn, while the transducer/stimulator and key supportfunctions are implanted within the auditory system. The externally wornportion communicates transcutaneously with the implanted portion toprovide audio signals that the implanted portion uses to stimulate tothe auditory system.

By way of example, one type of implantable transducer includes anelectromechanical transducer having a magnetic coil that drives avibratory actuator. The actuator is positioned to interface with andstimulate the ossicular chain of the patient via physical engagement.(See e.g., U.S. Pat. No. 5,702,342). In this regard, one or more bonesof the ossicular chain are made to mechanically vibrate, which causesthe ossicular chain to stimulate the cochlea through its natural input,the so-called oval window.

Implanted hearing devices are typically used by individuals withsignificant loss of hearing function or damage to the auditory system.As a result, they differ in the manner by which the signal is processedand delivered to the patient. The processing step, known in the art asSpeech Signal Processing (“SSP”), may include a number of steps such asamplification, frequency shaping, compression, etc. The steps in the SSPare determined by the design of the hearing device, while the particularinternal values used in the steps are generated from prescriptiveparameters determined by an audiologist. Once a speech processorreceives an audio signal (e.g., from a microphone) that is indicative ofambient acoustic signals, an drive signal produced and provided to animplanted stimulation device that stimulates the hearing impairedperson's auditory system. The auditory stimulation may be doneacoustically, mechanically, or electrically as a function of the typeand severity of the hearing loss in the hearing impaired individual.

The type and/or severity of hearing loss may dictate what type ofimplantable hearing device may be beneficial to an impaired person.Heretofore, this has required that many impaired persons utilizesemi-implantable hearing devices. Some surveys of current and potentialhearing instrument wearers show that fully implantable or non-visiblehearing devices have greater consumer acceptance. That is, there is somebelief that fully implantable hearing devices may avoid stigmatizingcosmetics associated with semi-implantable devices.

SUMMARY OF THE INVENTION

The present invention is generally directed to the provision of animplantable hearing unit that includes an implantable microphone, arechargeable power storage device, a speech signal processor (SSP). Thehearing unit further includes a signal coupling device that is adaptedfor electrical interconnection to an implanted auditory stimulationdevice, which is operative to stimulate an auditory component of apatient. Such an implanted auditory stimulation device may include,without limitation, cochlear implants, brain stem stimulation systems,auditory nerve stimulation systems, and middle ear or inner eartransducer systems. Stated otherwise, the stimulation device may be anydevice that is operative to acoustically, electrically and/ormechanically stimulate an internal component of the auditory system of apatient.

As noted, the hearing unit incorporates the implantable microphone, therechargeable power storage device and a signal processor. Thesecomponents may be housed in a common implant housing, or thesecomponents may be separate implantable devices that are electricallyconnectable. The hearing unit may also incorporate additional componentssuch as, but not limited to, memory devices, rectifying circuiting, etc.In any case, the implantable microphone is operative to transcutaneouslyreceive sound and generate an output signal. The processor utilizes theoutput signal to generate a drive signal for use in actuating animplantable auditory stimulator device. As may be appreciated, the drivesignal may be tailored to a particular stimulation device. The powerstorage device is operative to power the hearing unit as well as provideoperating power to the auditory stimulation device via the signalcoupling device. Further, the power storage device (e.g., one or morebatteries) is rechargeable using transcutaneously received signals froman external source. Such signals may include electromagnetic signals(e.g., RF signals) as well as magnetic signals (e.g., inductivesignals). Accordingly, the hearing unit may incorporate a receiver(e.g., coil or antenna) to receive such signals and/or a transmitter totransmit signals to an external receiver. To provide continuousoperation for extended periods of time, the rechargeable power storagedevice may have a capacity of at least 20 mW/h, more preferably at least50 mW/h and even more preferably at least 100 mW/h. However, it will beappreciated that use of the hearing unit with different stimulationdevices may result in different power requirements. Accordingly,capacity of the power supply may be selected in accordance with needs ofa particular system.

The signal coupling device is operative to provide processed drivesignals from the signal processor to the implantable stimulation device.Furthermore, the signal coupling device is also operative to providepower from the power storage device to the implantable stimulationdevice. The use of the signal coupling device to electrically power andprovide drive signals to an implanted stimulation device may allow forindependent/separate subcutaneous placement of those components. Thismay simplify placement of the stimulation device relative to an auditorycomponent of the patient. Further, the signal coupling device may allowfor selective removal of the implantable hearing unit without disturbingthe implantable stimulation device.

According to a first aspect of the present invention, an implantablehearing unit is provided that may be utilized with any of a variety ofdifferent implantable stimulation devices. In this first aspect, thesignal coupling device is a wireless signal transmitter utilized tointerconnect the hearing unit to the implantable stimulation device.That is, according to the first aspect a subcutaneously wireless link isestablished between two implantable devices, namely, an implantedhearing unit, which includes a microphone, power storage device andprocessor, and an implantable stimulation device. The wireless linkbetween the implanted hearing unit and the implantable stimulationdevice electrically interconnects those devices for power transferpurposes as well as for transferring processed signals (e.g., drivesignals) for use in auditory stimulation. In one arrangement, thewireless link comprises an inductive link. In such an arrangement, eachdevice will typically include a coil for use in inductivelytransmitting/receiving signals (e.g., drive signals and/or power). Suchsignals may be modulated and/or demodulate in any appropriate mannerincluding, without limitation, AM or FM modulation for analog signals aswell as sigma-delta or pulse-width modulation for digital signals. FIG.2B depicts a modulator 151 in black-box format that accomplishes theaforementioned modulation.

In one arrangement, use of the wireless signal coupling device with theimplantable hearing unit may allow for retrofitting existingsemi-implanted hearing instruments. Accordingly, such instruments may beconverted from partially implanted hearing instruments into fullyimplanted hearing instruments. In this regard, the signal processor ofthe implantable hearing unit may be programmed to provide drive signalsthat are compatible with an existing implantable stimulation device(e.g., cochlear stimulation devices and/or middle ear devices). In suchan application, removal of an implantable stimulation device alreadyinterconnected to a component of a patient's auditory system is notrequired to convert the device to a fully implantable hearing system. Aswill be appreciated, different implantable stimulation devices may beinterconnected to auditory components in a manner that makes theirremoval undesirable and/or potentially damaging. For instance, removalof an electrode array of a cochlear implant would require surgery undergeneral anesthesia and may cause damage to the cochlea thereby renderingthe cochlea unable to utilize such an implant. Likewise, some middle eartransducers are affixed to one or more of the ossicle bones and mayrequire removal of one or more ossicle bones, or cause damage to theossicles, upon explanation. In either case, it is undesirable to removeimplanted stimulation device.

However, many semi-implantable devices already include a wirelessreceiver (e.g., coil) that is operative to receive transcutaneoussignals from an external speech processing unit. Accordingly, a wirelesstransmitter (e.g., an inductive coil) of the implantable hearing unitmay be positioned relative to the wireless receiver of the implantablestimulation device upon implantation of the implantable hearing unit.This may effectively retrofit an existing semi-implantable hearinginstrument such that it becomes a fully implantable hearing instrument,in a minimally invasive procedure, preferably under local anesthesia. Topermit such positioning, the wireless transmitter may be interconnectedto the hearing unit using a flexible connector.

In another arrangement of the present aspect, the wireless signalcoupling device may be utilized with originally manufactured implantablehearing systems having two separate implantable portions. In thisregard, a first portion of the implantable system may comprise theimplantable stimulation device, which may be intended for long term orsubstantially permanent implantation. A second portion of implantablesystem may comprise the hearing unit that supports power, microphone andspeech processing capabilities. The second portion of the implantablesystem may be conveniently located such that is more easily accessiblefor replacement and/or upgrade. Preferably, the second portion may beaccessible under local anesthesia. Likewise, the wireless signalcoupling device may permit the first portion of the implantable systemto be located relative to a given auditory component with less concernabout future access. In any case, the two-portion fully implantablesystem that utilizes a wireless signal coupling device may permit easyaccess and servicing of the hearing unit without disturbing thestimulation device; thus, the difficulty and risk of disturbing thedelicate structures of the middle or inner ear may be avoided.

According to another aspect of the present invention, an implantablemodule or hearing unit, which provides power, microphone and signalprocessing functions, is interconnected to an implantable cochlearstimulation device by a conductive signal coupling device. Such aconductive signal coupling device may include a flexible communicationswire. Such a flexible communications wire may facilitate positioning ofthe hearing unit of a stimulation device. Importantly, the conductivesignal coupling device includes a detachable connector that allows forselective disconnecting of the implantable hearing unit and theimplantable cochlear stimulation device. As will be appreciated, thecochlear stimulation device will include an electrode array that isadapted for insertion into the cochlea of the patient. Once insertedinto the cochlea, it is desirable that disturbance of the electrodearray be minimized. Accordingly, use of the selectively detachableconnector permits removal of the implantable hearing unit withoutremoval or disturbance of the implantable cochlear stimulation device.

Any appropriate conductive signal coupling device may be utilized.Generally, the conductive signal coupling device will include at least afirst communications wire that extends from one of the implantablehearing unit or the implantable stimulation device. Such acommunications wire extending from one of the implantable devices mayplug into the other device, or, communications wires from each devicemay be connected by a connector disposed between the devices. Theconnector may be of any appropriate type. In one embodiment, apacemaker-style, or “IS-1” connector is utilized. However, it will beappreciated that any connector that is operative for use in animplantable environment may be utilized. While any appropriatecommunications wire(s) may be used to interconnect the implantablehearing unit and the implantable stimulation device, it may be desirableto reduce the number of conductors (e.g., leads) interconnecting the twoimplantable devices to simplify the mechanical connector. For instance,in one embodiment a two conductor communications wire may be utilized.

In order to transmit appropriate levels of data between the implantablehearing unit and the implantable stimulation device, especially whenusing a reduced number of conductors, modulation and demodulation of thesignals may be required. As will be appreciated, some implantablestimulation devices utilized multiple channels and or electrodes (e.g.,24 electrodes) for stimulation purposes. In this regard, it may benecessary to convey a relatively large quantity of drive signalinformation for use in stimulating patient auditory component.Compression, modulation and/or demodulation of signals sent acrosscommunications wire may be required. Examples of such modulation in themodulation schemes include, without limitation, Frequency DivisionMultiplexing (FDM) and Time division Multiplexing (TDM).

According to another aspect of the present invention, a method isprovided for wirelessly interconnecting an implantable hearing unit withan implantable stimulation device. The method includes the steps ofpositioning an implantable hearing unit relative to an implantablestimulation device. Once positioned, a wireless signal coupler generatesa wireless link that electrically interconnects the hearing unit to thestimulation device to permit the transmission of power and drive signalstherebetween. Accordingly, once the implantable hearing unit iswirelessly interconnected to the implantable stimulation device, thehearing unit may generate drive signals and provide such drive signalsto the stimulation device via a subcutaneous wireless link. Inconjunction with providing drive signals, the hearing unit may alsoprovide power over to the wireless link. The provided power may allowthe stimulation device to operate and utilizes the drive signal tostimulate an auditory component of a patient.

The step of positioning may entail positioning a wireless transmitterassociated with the implantable hearing unit relative to a wirelessreceiver associated with the implantable stimulator. For instance, thewireless transmitter and wireless receiver may be disposed in asubstantially face-to-face relationship such that an inductive couplingmay exist therebetween. However, it will be appreciated that thewireless transmitter and wireless receiver need not be in direct contactand may be separated. What is important is that the wireless transmitterand wireless receiver are operative to subcutaneously exchange signals.

The step of positioning may be performed during a surgical procedurewherein one or both of the implantable hearing unit and implantablestimulation device are implanted. Alternatively, step the positioningmay be performed where the implantable hearing unit is implantedrelative to a previously implanted stimulation device.

According to another aspect of the present invention, a method forelectrically interconnecting first and second separate modules of afully implantable cochlear hearing instrument is provided. The methodincludes positioning a cochlear stimulation device (e.g., a firstmodule) relative to the first subcutaneous location on the body of apatient (e.g., relative to the cochlea). The method further includespositioning an implantable hearing unit (e.g., a second module) relativeto a second subcutaneous location on the body of a patient. Once thecochlear stimulation device and the implantable hearing unit arepositioned relative to the first and second subcutaneous locations, asignal coupling device, such as a communications conductor or wire, issubcutaneously routed between the implanted hearing unit and implantedcochlear stimulation device. The communications wire may releasablyconnect the implantable hearing unit and stimulation device to permitremoval of one module without requiring removal of the other module.

According to another aspect of the present invention, a method for usewith an implantable auditory stimulation device is provided. The methodincludes generating a drive signal at a first subcutaneous implantmodule where the drive signal is operative to actuate an implantableauditory stimulation device. The method further includes wirelesslytransmitting the drive signal from the first subcutaneous implant moduleto a second subcutaneous implant module associated with an implantableauditory stimulation device. Accordingly, the method may further includeactuating the auditory stimulation device according to the drive signal.Generating the drive signal may further include receiving sound at asubcutaneous microphone and generating an output associated with thatsound. This microphone output may then be processed to generate thedrive signal.

Wirelessly transmitting the drive signal may include generating aninductive coupling between the first module and the second modulewherein magnetic signals may be exchanged therebetween or creating an RFlink between these modules such that electromagnetic signals may beexchanged therebetween. In any case, the method may further includewirelessly transmitting power from a power supply associated with thefirst implant module to the second implant module. Preferably, thispower supply should be sufficient to run the second implant module andan associated auditory stimulation device associated therewith. In onearrangement, wirelessly transmitting power may include transmittingpower sufficient to operate the second module and the auditorystimulation device for at least eight hours. In a further arrangement,the transmitted power may be sufficient to operate the device for atleast 12 hours and, in a yet further arrangement, at least 16 hours.

In order to provide power for the second implant module, the method mayfurther include recharging the power supply associated with the firstimplant module. Such recharging may occur periodically and may entailthe transcutaneous receipt of at least one of electromagnetic signalsand magnetic signals. In any case, the received signals are utilized tocharge the power supply. Accordingly, it will be appreciated that, inorder to provide a continuous power supply for a predetermined period oftime, it may further include the selection of a power supply having apredetermined capacity, wherein that capacity allows for a continuousexpected discharge over the period of time.

The drive signals that are generated by the first implant module mayinclude signals that are specific to a given implantable stimulationdevice. For instance, such signals may include signals that may beutilized for actuating an intracochlear electrode, a middle eartransducer, an inner transducer, etc.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a semi-implantable cochlear implant;

FIG. 2A illustrates an implantable portion of a cochlear implant and animplantable hearing unit.

FIG. 2B illustrates a schematic diagram of the components of FIG. 2A.

FIG. 3 illustrates the implantable portion of the cochlear implant andthe implantable hearing unit of FIG. 2 in an overlying relationship.

FIGS. 4 and 5 illustrate a fully implantable cochlear implant having twoseparate implantable modules that are interconnected with a detachablecommunications wire.

FIG. 6 illustrates a cranial placement of the components of FIG. 2A.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made to the accompanying drawings, which at leastassist in illustrating the various pertinent features of the presentinvention. In this regard, the following description of a hearinginstrument is presented for purposes of illustration and description.Furthermore, the description is not intended to limit the invention tothe form disclosed herein. Consequently, variations and modificationscommensurate with the following teachings, and skill and knowledge ofthe relevant art, are within the scope of the present invention. Theembodiments described herein are further intended to explain the bestmodes known of practicing the invention and to enable others skilled inthe art to utilize the invention in such, or other embodiments and withvarious modifications required by the particular application(s) oruse(s) of the present invention.

FIGS. 1-3 illustrate one application of the present invention. Asillustrated, a first application is directed to converting an existingsemi-implantable hearing instrument into a fully implantable system.However, certain aspects of the present application have applicationbeyond conversion of a semi-implantable hearing system into a fullyimplantable system. For instance, certain aspects may be utilized withoriginally manufactured implantable hearing instruments. It will befurther noted that though the invention is shown in use for converting asemi-implantable cochlear implant into a fully implantable cochlearimplant, the present invention may be employed in conjunction with othersemi-implantable hearing instruments as well as, including, withoutlimitation auditory brain stem stimulation systems, auditory nervestimulation systems, and middle ear transducer systems. In this regard,the present invention has applicability with electrical stimulationsystems as well as mechanical stimulation systems. Auditory stimulationdevices that may be utilized with aspects of the present inventioninclude those discussed in U.S. Pat. Nos. 5,545,219, 5,624,3765,277,694, 5,913,376, 5,984,859, 6,315,710, 6,491,622, 6,517,476,6,575,894, 6,676,592 and 6,726,618 the contents of which areincorporated by reference herein. Therefore, the illustrated applicationis for purposes of illustration and not limitation.

Generally, there are three main parts of the cochlear implant. There isan implant receiver/stimulator 200 that is implanted on a patient'sskull, an electrode array 210 that extends from the housing of thereceiver/stimulator 200 into the cochlea 250, and an external speechprocessing unit 220. See FIG. 1. One exemplary receiver/stimulator isthe Nucleus made by Cochlear Limited of Australia. The external speechprocessing unit may comprise one or more parts depending upon thecochlear implant. For instance, the external speech processing unit maybe an integrated behind the ear unit that includes a microphone, aspeech processor, a transmitting coil, and a power source (e.g.,batteries). Alternatively, the external speech processing unit mayinclude a wearable processing unit/power unit 220 that is connected(e.g., wired) to a behind the ear unit 224. Such a behind the ear unitwill typically include a microphone 226, a transmitting coil 228 and oneor more magnets for retentive positioning with the receiver/stimulator200. Such a separate processing unit/power unit 220 may beinterconnected to patients' clothes, belt, etc.

In any case, the microphone 226 worn behind the patient's ear performsthe function of the outer ear. That is, the microphone 226 picks upambient sounds for processing. As noted, the speech processor may bemounted behind the ear or worn externally (e.g., on a belt or in apocket etc). The speech processor, based on previous fittings selectsthe sounds most useful for understanding speech and codes themelectronically. The electronic codes or drive signals are sent back tothe transmitting coil 228, which is generally located behind or beneaththe microphone 226. The transmitting coil 228 is held in place by twomagnets, one located under the skin near the receiver/stimulator 200 andthe other in the center of the behind the ear unit 224. The transmittingcoil 228 sends the drive signals through the skin via inductive couplingto a receiving coil 202 of the implanted receiver/stimulator 200. Thereceiver/stimulator 200 converts the drive signals it receives intoelectrical signals that it sends along the electrode array 210, which isimplanted in the cochlea 250 of the user.

The electrode array 210 generally consists of a plurality of smallelectrode bands (e.g., 24) arranged in a row inside an a flexibleextension. Each individual electrode has a wire connecting it to thereceiver/stimulator; each has been separately programmed to deliverelectrical signals representing sounds that can vary in loudness andpitch. When the electrodes receive an electrical signal, they stimulatethe appropriate populations of auditory nerve fibers, which send themessages to the brain. One advantage of such a multi-channel cochlearimplant is that speech can be filtered into frequency bands by thespeech processor and delivered to different points along the cochlea.Generally, the more electrodes (i.e., channels) included within thearray, the better resulting sound quality a user can expect.

The cochlea is organized so that different sound frequenciespreferentially stimulate different hair cells. (As the membrane alongthe bottom of the cochlea resonates in time with the sound vibration,hair cells at different positions along the membrane are stimulated.)Stimulating hairs located at the base of the cochlea producesperceptions of high-pitched sounds; stimulating hairs located at theopposite end (apex) of the cochlea produces perceptions of lower-pitchedsounds. Accordingly, the cochlear implant has a number of electrodes atdifferent positions on the cochlea and is designed to deliver stimuli toappropriate electrodes so that high-pitched sounds cause electrodes tostimulate hair cells towards the base of the cochlea and low-pitchedsounds cause electrodes to stimulate hair cells towards the apex of thecochlea.

FIGS. 2A and 2B, illustrate an implantable hearing unit 100 that may beutilized with the receiver/stimulator 200 of the semi-implantablecochlear implant of FIG. 1 to create a fully implantable hearinginstrument. As shown, the implantable hearing unit 100 includes abiocompatible implant housing 110 that is adapted to be locatedsubcutaneously on a patient's skull. The hearing unit 100 includes afirst receiving coil 118, a second transmitting coil 122, a signalprocessor 150 (e.g., disposed within the housing 100) and a microphone120. It will be appreciated that each coil 118 and 122 is capable ofinductively transmitting and receiving signals and that the terms‘receiving coil’ and ‘transmitting coil’ are utilized for purposes ofclarity and not by way of limitation. The receiving coil 118 isoperative to transcutaneously receive electrical power and/orprogramming. Further, the coil 118 may provide information to anexternal processor. The transmitting coil 122 is operative to provideelectrical power and drive signals to an implanted stimulator, as willbe more fully discussed herein.

The microphone 120 is interconnected to the implant housing 110 via acommunications wire 124. This allows the microphone 120 to besubcutaneously positioned to receive acoustic signals through overlyingtissue. However, it will be appreciated that in other embodiments amicrophone 130, as shown in phantom, may be integrated into the implanthousing 110. The implant housing 110 may be utilized to house a numberof components of the implantable hearing unit 100.

FIG. 2B schematically illustrates one embodiment of the internalcomponents of the hearing unit 100 and stimulation device 200 of FIG.2A. However, in the illustrated embodiment the implant housing 110houses both the receiving coil 118 and the transmitting coil 122. Asshown, the implantable hearing unit 100 and the stimulation device 200are located subcutaneously beneath the skin 170 of a patient. Further,the implant housing 110 also houses a number of additional components ofthe hearing unit 100. Specifically, the housing 110 includes a signalprocessor 150, a communications processor 152, audio input circuitry154, an internal power supply or battery 140, a power management unit142 and manufacture specific drive logic and/or circuitry 156.

As shown, the internal battery 140 is interconnected to the powermanagement unit 142. The power management unit 142 is operative toprovide power for the implantable hearing unit as well as providenecessary rectifying functionality for use in charging the internalbattery 140. Such charging utilizes transcutaneously received signalsfrom an external unit 160, where the signals are received via thereceiving coil 118. Of note, the hearing unit 100 may furtherincorporate one or more external batteries 144, which may be operativelyinterconnected to the power management unit 142. This may allow thehearing unit 100 to have a power capacity that permits uninterrupted useof the implant auditory stimulation device 200 for extended periods oftime.

The audio input circuitry 154 is operative to receive an output signalfrom the implantable microphone 120 and provide this output signal tothe signal processor 150. The audio input circuitry 154 may performvarious filtering and/or amplification processes on the microphoneoutput signal. In any case, the signal processor 150 utilizes thereceived microphone output signal for use in generating a drive signalfor receipt by the auditory stimulation device 200. In this regard, thesignal processor 150 may utilize manufacture specific drive logic and/orcircuitry to generate a drive signal that is compatible with aparticular auditory stimulation device 200. Such a drive signal, as wellas power from the internal battery 140 and/or an external battery 144may then be wirelessly provided to the auditory stimulation device 200utilizing the transmitting coil 122. Alternatively, and as will bediscussed herein, the drive signals and power may be provided to thestimulation device 200 utilizing a conductor 320 that extends betweenthe housing 110 of the hearing unit 100 and the auditory stimulationdevice 200.

An external unit 160, which includes a coil 162 for inductively couplingto the receiving coil 118 of the hearing unit 100, is utilized toprovide energy to the hearing unit 100 for use in recharging the batteryor batteries of the hearing unit 100. Further, the external unit 160 mayalso be operative to provide programming instructions and/or controlinstructions to the hearing unit 100. In this regard, a communicationsprocessor 152, which may in other embodiments be incorporated into thecommon processor with the signal processor 150, is operative to receiveprogram instructions from external unit 160 as well as provide responsesto the external unit 160. As may be appreciated, various additional ordifferent processing logic and/or circuitry components may be includedin the implant housing 110 as a matter of design choice.

In the embodiment of FIGS. 2A and 2B, the signal processor 150 withinthe implant housing 110 communicates with the implantreceiver/stimulator 200 via a subcutaneous inductive link. Morespecifically, the transmitting coil 122 of the implantable hearing unit100 is adapted to crate an inductive link with the receiving coil 202 ofthe implant receiver/stimulator 200. Specifically, the transmitting coil122 is configured to be disposed in an overlying relationship with thereceiving coil 202 of the implant receiver/stimulator 200. See FIGS. 2Aand 3. In the present embodiment, the transmitting coil 122 isinterconnected to the implant housing 100 via a flexible communicationswire 126 to permit the transmitting coil 122 to be more easilypositioned relative to the receiving coil 202 of the implantreceiver/stimulator 200. Mating magnets 108, 208 may be used to positionthe coils 122, 202. Though shown in a direct face to face relationship,it will be appreciated that the transmitting coil 122 of the implantablehearing unit 100 and the receiving coil 202 of the implantreceiver/stimulator 200 may be at least partially separated so long asthey maintain an inductive link.

During normal operation, acoustic signals are received subcutaneously atthe microphone 120 and the microphone provides audio signals to theimplantable hearing unit 100. The signal processor 150 within thehousing 110 of the implantable hearing unit 100 processes the receivedaudio signals to provide a processed audio signal (e.g., a drive signal)for transmission to the receiver/stimulator 200 via the subcutaneousinductive link between coils 122 and 202. As will be appreciated, theimplantable hearing unit 100 may utilize digital processing techniquesto provide frequency shaping, amplification, compression, and othersignal conditioning, including conditioning based on patient-specificfitting parameters in a manner substantially similar to an externalspeech processing unit (e.g., 220 of FIG. 1). The implantedreceiver/stimulator 200 receives drive signals from the implantablehearing unit 100 that are substantially identical to drive signalsreceived from the external speech processing unit 220. Accordingly, theimplanted receiver/stimulator 200 converts the drive signals it receivesinto electrical signals that are sent to the electrode array 210, whichstimulates the patient's cochlea and causes the sensation of sound.

To power the fully implantable hearing instrument system, theimplantable hearing unit 100 generally utilizes an external charger unit160 (See FIG. 2B) to recharge one or more energy storagedevices/batteries 140, 144 that may be disposed within or otherwiseconnected to the implant housing 100. In this regard, the externalcharger may be configured for disposition behind the ear of the implantwearer in alignment with the receiving coil 118 of the implant housing100. The external charger and the implant housing 100 may each includeone or more magnets to facilitate retentive juxtaposed positioning. Suchan external charger may provide power inductively. In anotherarrangement, not shown, the external unit is operative totranscutaneously transmit RF signals (e.g. electromagnetic signals) to areceiver. In this arrangement, the receiver may also include, forexample, rectifying circuitry to convert a received signal into anelectrical signal for use in charging the energy storagedevice/batteries.

As will be appreciated, the use of the inductive link between theimplantable hearing unit 100 and the receiver/stimulator 200 facilitatesremoval of the hearing unit 100 for servicing, upgrades etc. In thisregard, one drawback of cochlear implants is that once electrode array210 is inserted into the cochlea 250, subsequent removal of theelectrode array 210 may result in damage to the cochlea 250.Accordingly, by utilizing the inductive link, the implantable hearingunit 100 may be removed for servicing without disturbing thereceiver/stimulator 200 and/or the electrode array 210.

Of note, the system of FIGS. 1-3 may be utilized not only in retrofitapplications where a semi-implantable hearing aid is converted into afully implantable hearing aid, but also in new hearing instrumentsystems where it may be desirable to have an implantable portion (e.g.,hearing unit 100) that is selectively removable without disturbing amore permanently implanted device (e.g., stimulator).

FIGS. 4 and 5 illustrate a second application of the present invention.In this application, the implantable hearing instrument system utilizesmost of the same components of the implantable hearing unit 100 asdiscussed in relation to FIGS. 2-3 above. However, in this applicationthe implantable hearing unit 100 is directly electrically connected tothe implantable stimulator 300. Specifically, the stimulator 300 andimplantable hearing unit 100 are connected via a communications wire 320instead of by a subcutaneous inductive link. In this regard, a receivingcoil is not needed for the stimulator 300 nor is a transmitting coilrequired for the implantable hearing unit 100. Otherwise, the structureand function of stimulator 300 is substantially the same as stimulator200. Again, an electrode array 310 extends from the stimulator 300 andthe stimulator 300 provides drive signals to the electrode array 310 isin manner that substantially unchanged in relation to that discussedabove.

Though the stimulator 300 and implantable hearing unit 100 areinterconnected by a communications wire 320, the communications wire 320includes a detachable connector 340 that permits selective detachment ofthe communications connection between the stimulator 300 implantablehearing unit 100. In this regard, implantable hearing unit 100 may bedetached from the stimulator 300 and its attached electrode array 310.As noted above, it may be undesirable after implant to remove thestimulator 300 and electrode array 310 as the potential to damage to thecochlea exists. However, it is foreseeable that one or more componentsof the implantable hearing unit 100 may require periodic maintenance,updating and/or replacement. For instance, while it is believed that theonboard power storage device will last for a number of years, it mayeventually need to be replaced. It is further believed that advancementsto hardware and/or software may become available in the future and itmay be desirable to replace the entire implantable hearing unit 100 toupgrade the system. In any case, use of the detachable connector 340 inthe communications wire 330 allows for such removal and/or maintenanceof the hearing unit 100 without disturbing the electrode array 320.

Of note, cochlear implants typically utilize a plurality of electrodesthat are each interconnected to be stimulator by an individual conductor(i.e. wire). That is, a number of wires may extend from the stimulator300 that is equal to the number of electrodes (e.g., 22 electrodes and22 wires) of the cochlear implant. However, it is generally undesirableto have a connector 340 that includes such a large number of conductiveconnections. More preferably, a communications wire 320 having fewer(e.g., two) conductors may be utilized to simplify the connector 340. Aselectively detachable connector that provides at least two conductorconnection and which is suited for implantation uses is described inU.S. Pat. No. 6,517,476 entitled “Connector for Implantable Hearing Aid”the contents of which are incorporated by reference herein.

In order to properly stimulate the patient's auditory system, thestimulator 300 must receive adequate information for all the electrodesor channels across the communications wire 320. Use of a two conductorwire generally requires modulating/demodulating of the signals sent fromthe implantable hearing unit 100 to the stimulator 300 to allow foradequate data transfer. For instance, Frequency Division Multiplexing(FDM) and Time Division Multiplexing (TDM) and or Code DivisionMultiplexing (CDMA) modulating/demodulating methodologies may beutilized in order to provide adequate information to the stimulator.

In any arrangement, (e.g., wireless connection or direct conductivecoupling) the capacity of the power storage device(s) of the implantablehearing unit 100 will determine the length of time a user may go betweennecessary recharges. The capacity of a battery is generally stated inmilliampere-hours, or mAh. This parameter defines the length of time thebattery may deliver a given rate of current or, conversely, the maximumcurrent deliverable over a fixed period. Although these two measures arenot strictly interchangeable over all rates of discharge, theycorrespond well enough to permit designers to selected batteries thatare sized for different applications.

It has been determined that inductive/RF transmission efficiency is asignificant factor in determining time between battery charges insystems that utilize an inductive/RF power/signal link to provide powerand drive signals to an implanted auditory stimulation device. The timebetween charges for an implantable battery connected by such a link maybe calculated as:

$\begin{matrix}{T_{bc} = {\frac{Q}{I_{proc} + \frac{I_{stim}}{\eta_{RF}}}.}} & {{Eq}.\mspace{14mu} 1}\end{matrix}$where T_(bc) is time between charges, Q is battery capacity, I_(proc) isthe current drain of the processor connected to the battery, I_(stim) isthe current drain of the auditory stimulation device driven through thelink, and η_(RF) is the efficiency of the inductive/RF link.

As an example, assume that the battery capacity is 50 mAh, currentrequirement for the sound processor is 1.5 mA, current requirement for acochlear stimulator is 2.5 mA, and inductive RF link efficiency is 40%.

Battery capacity 50 mAh Current drain before RF link (processor) 1.5 mACurrent drain after RF link (stimulator) 2.5 mA RF link efficiency 40%Resulting time between charges 6.45 hrsThe RF efficiency of 40% assumed in the example above is typical of RFtransmission architectures. The resulting time between charges of lessthan 6½ hours may be less than is desired by many users, who may preferthat a fully implantable system permit a full day of use without theinconvenience of recharging the implantable battery.

User needs may thus be compromised by the energy losses associated withinductive coupling. While the use of a conductive coupling eliminatesthe inefficiency of the inductive coupling, this is not an upgradeoption for existing users. In this regard, the remaining option toextend the time between recharge is to increase the capacity of thebattery or batteries of the implantable hearing unit 100.

As shown above, the amount of battery capacity may be selected based onthe type of implantable auditory stimulation device utilized and thedesired time between capacity. Accordingly, for instances where lowbattery capacities are sufficient, a rechargeable battery 140 may beincorporated into the housing 110 of the implantable hearing unit 100.See FIG. 2B. This may result in a compact hearing unit 100. For such acompact system, a convenient location for placement of the is in thetemporal region of the skull, near the typical location of thestimulator. See FIG. 6. This location minimizes the length of exposedwires 124, 126, and simplifies the surgical procedure.

In instances where greater battery capacity is required, a largerbattery, or multiple batteries may be utilized. Again, a rechargeablebattery or batteries may be incorporated into the housing 110 of theimplantable hearing unit 100 and/or one or more separate implantablebatteries 144 that are electrically connected to the implantable hearingunit 100 may be utilized. As will be appreciated, such separateimplantable batteries may be detachable such that the battery orbatteries may be removed and replaced without removing the implantablehearing unit 100. However, the use of larger or multiple batteries mayincrease the size of the implantable hearing unit making craniallocation of the implantable hearing unit problematic.

In instances in which the implantable hearing unit or implantablebatteries are too large for convenient placement on the skull,implantable hearing unit 100, including, for example, the receiving coil118 and batteries may be placed subclavicularly, in a location similarto that of an implantable pacemaker. In this arrangement, the wire 124and 126 extending between the hearing unit 100 and the microphone 120and transmitting coil 122, respectively, may be routed subcutaneouslythrough the soft tissues of the neck. Such an arrangement may allow forconverting an existing partially implantable hearing instrument into afully implantable hearing instrument that provides full day use (e.g.,15-16 hours) between recharges.

Those skilled in the art will appreciate variations of theabove-described embodiments that fall within the scope of the invention.As a result, the invention is not limited to the specific examples andillustrations discussed above, but only by the following claims andtheir equivalents.

What is claimed:
 1. An implantable hearing prosthesis, comprising: afirst implantable apparatus including an implantable signal processorconfigured to generate drive signals for activating an implantableauditory stimulation device; a second implantable apparatus includingthe implantable auditory stimulation device; and a flexiblecommunications device extending between said first implantable apparatusand said second implantable apparatus; and a selectively attachable anddetachable connector configured to mechanically connect and disconnectthe communications device from one of the first implantable apparatus orthe second implantable apparatus, wherein said first implantableapparatus further comprises a modulator configured to modulate saiddrive signals prior to said drive signals being transmitted to saidimplantable stimulation device, wherein the implantable auditorystimulation device is a cochlear electrode array configured forinsertion into a cochlea of a recipient, and said drive signals drivethe cochlear electrode array to stimulate the cochlea with electricalcurrent.
 2. The implantable hearing prosthesis of claim 1, wherein: thefirst implantable apparatus is an implantable module including: theimplantable signal processor; an implantable microphone operative totranscutaneously receive sound and generate a microphone output signal;and an implantable rechargeable battery for powering at least saidmicrophone and said processor.
 3. The implantable hearing prosthesis ofclaim 1, wherein: said first implantable apparatus further comprises ademodulator for demodulating modulated drive signals.
 4. The implantablehearing prosthesis of claim 1, wherein: said connector includes only twoelectrical contact conductors.
 5. The implantable hearing prosthesis ofclaim 1, wherein: communication between the first implantable apparatusand the second implantable apparatus is established by an inductivelink, wherein the link is established by a transmitting coil and areceiving coil, wherein the transmitting coil is removably mated withthe receiving coil, and wherein the transmitting coil and the receivingcoil are configured to be completely implantable.
 6. The implantablehearing prosthesis of claim 1, wherein: the first implantable apparatusis configured to provide a modulated signal modulated by the modulatorto the flexible communications device; and the flexible communicationsdevice is configured to communicate the modulated signal from the firstimplantable apparatus to the second implantable apparatus.
 7. Theimplantable hearing prosthesis of claim 1, wherein: the flexiblecommunications device is configured to deliver modulated signalsmodulated by the modulator from the first implantable apparatus to thesecond implantable apparatus.
 8. The implantable hearing prosthesis ofclaim 1, wherein: the implantable hearing prosthesis is configured tomodulate said drive signals prior to said drive signals beingtransmitted to said second implantable apparatus via said flexiblecommunications device.
 9. A method, comprising: positioning a firstcomponent of an implantable hearing prosthesis at a first subcutaneouslocation in a recipient, said first component including an implantableauditory stimulation device; positioning a second component of theimplantable hearing prosthesis at a second subcutaneous location in arecipient, the second component including an implantable signalprocessor configured to generate drive signals for activating theimplantable auditory stimulation device; releasably mechanicallyconnecting said first and second components utilizing a communicationsconductor configured to establish communication between the first andsecond component; evoking a hearing percept as a result of transmissionof drive signals from the second component to the first componentthrough the communications conductor; and after evoking the hearingpercept, removing the second component from the recipient and locating athird component at a subcutaneous location in the recipient, the thirdcomponent including a third implantable signal processor configured togenerate drive signals for causing the implantable auditory stimulationdevice to evoke a hearing percept.
 10. The method of, claim 9, furthercomprising: releasing the communications conductor from at least one ofthe first or second components; and releasably mechanically connectingthe first and third components utilizing the communications conductor.11. The method of claim 9, wherein: the first component includes areceiver and an intracochlear electrode; and the second component is amodule that includes an implantable microphone, a rechargeable powersupply and a processor.
 12. The method of claim 9, further comprising:subcutaneously routing the communications conductor to a locationextending between said first and second components.
 13. The method ofclaim 11, further comprising: transmitting from said second component tosaid first component, through said communications conductor, signals foruse in actuating said intracochlear electrode.
 14. The method of claim9, wherein the implantable auditory stimulation device includes acochlear electrode array including at least 22 electrodes, and whereinthe action of releasably mechanically connecting comprises establishingcommunication between said first and second components via only twoconductors.
 15. The method of claim 9, further comprising: afterreleasably mechanically connecting said first and second components,releasing the connection while at least the first component is implantedin a recipient.
 16. A method, comprising: positioning a first componentof an implantable hearing prosthesis at a first subcutaneous location ina recipient, said first component including an implantable auditorystimulation device; positioning a second component of the implantablehearing prosthesis at a second subcutaneous location in a recipient, thesecond component including an implantable signal processor configured togenerate drive signals for activating the implantable auditorystimulation device; and releasably mechanically connecting said firstand second components utilizing a communications conductor configured toestablish communication between the first and second component, whereinthe action of releasably mechanically connecting said first and secondcomponents utilizing a communications conductor configured to establishcommunication between the first and second component occurs while atleast the first component is implanted in a recipient.
 17. Animplantable hearing prosthesis, comprising: a first implantableapparatus including an implantable signal processor configured togenerate drive signals for activating an implantable auditorystimulation device; a second implantable apparatus including theimplantable auditory stimulation device; and a flexible communicationsdevice extending between said first implantable apparatus and saidsecond implantable apparatus; and a selectively attachable anddetachable connector configured to mechanically connect and disconnectthe communications device from one of the first implantable apparatus orthe second implantable apparatus, wherein said first implantableapparatus further comprises a modulator configured to modulate saiddrive signals prior to said drive signals being transmitted to saidimplantable stimulation device; and wherein the implantable hearingprosthesis further comprises: a third implantable apparatus including animplantable microphone; and a second communications device separate fromthe flexible communications device, the second communications deviceconfigured to communicate electrical signals from the third implantableapparatus to the first implantable apparatus.